High-speed polysilicon resonant-cavity photodiode with SiO/sub 2/-Si Bragg reflectors

Previously, it has been shown that the bandwidth of Si photodiodes can be increased by more than an order of magnitude, without sacrificing responsivity, by a resonant-cavity structure that utilized GeSi-Si asymmetric Bragg reflectors. In this letter, we report an interdigitated p-i-n polysilicon resonant-cavity photodiode, which employs a Si-SiO/sub 2/ Bragg reflector, that is more compatible with standard Si processing technology. For an absorbing region thickness of only 0.5 /spl mu/m, a peak quantum efficiency of 40% was achieved and the dark current was <60 nA at 10 V. For 2 /spl mu/m/spl times/2-/spl mu/m finger width and spacing the bandwidth was 10 GHz.